1. Field of the Invention
The present invention relates to a process for the preparation of polyether-ester polyols. More particularly, the invention relates to the preparation of these polyols employing certain alkylamines as catalysts therefor.
2. Prior Art
The preparation of polyether-ester polyols by the reaction of an alkylene oxide with a half-acid ester obtained by the reaction of a polyol with an unsaturated polycarboxylic acid anhydride is well known in the art as evidenced by inter alia U.S. Pat. Nos. 3,459,733; 3,585,185; 3,639,541 and 3,639,542. The latter three patents also teach that trialkylamines may be employed as catalysts for the reaction in amounts ranging from 0.2 percent to 2.5 percent by weight based on the weight of the starting polyol. However, use of these amounts of trialkylamines results in products having poor color quality affecting their utility as reactants in the preparation of polyurethane foams. Accordingly, it is conventional in the art to prepare polyether-ester polyols either in the absence of catalysts or in the presence of inorganic alkaline catalysts. Both alternatives create problems, the former requiring almost twice the reaction time while the latter involves difficult and costly catalyst removal operations.